114 METALS AND THEIR COMBINATIONS. 



bluish- white, or dark gray ; a few metals show a distinct color, 

 as, for instance, gold and calcium (yellow), copper (red). 



At ordinary temperatures metals are solids with the exception 

 of mercury, all are fusible, and some are so volatile that they 

 may be distilled. Most, probably all, metals may be obtained 

 in a crystallized condition. 



The combinations of metals among themselves are called 

 alloys, or, when mercury is one of the constituents, amalgams. 

 These combinations, which may usually be obtained by fusing 

 the metals together, must be looked upon as molecular mix- 

 tures, not as definite chemical compounds. All alloys still ex- 

 hibit the metallic nature in their general physical characters. 

 It is different, however, when metals combine with non-metals ; 

 in this case the metallic characters are almost invariably lost. 



All metals combine with chlorine, fluorine, and oxygen ; most 

 metals also with sulphur, bromine, and iodine, forming the 

 respective chlorides, fluorides, oxides, sulphides, bromides, and 

 iodides. 



Most metals may be obtained from their oxides by heating 

 the same with charcoal, the carbon combining with the oxygen 

 of the oxide, whilst the metal is liberated : 



MO + C = CO + M ; 

 Or 



2MO + C = CO, + 2M. 



QUESTIONS. 



171. How many metals are known, and about how many are of 

 general interest ? 



172. Mention some metals showing very low and some showing very 

 high fusing-points. 



173. What range of specific gravities do we find among the metals ? 



174. Mention some^univalent, some bivalent, and some metals show- 

 ing a different valence under different conditions. 



175. Mention some metals which are found in nature in an uncom- 

 bined state ; some which are found as oxides, sulphides, chlorides, and 

 carbonates, respectively. 



176. Into what two groups are the metals divided ? 



177. State the three groups of light metals. 



178. What is a metal ? 



179. What is an alloy, and what an amalgam ? 



180. By what process can most metals be obtained from their oxides ? 



